Pothead



J. O. JACKSON June 9, 1953 POTHEAD 2 Sheets-Sheet 1 Filed April 5. 1948 June 9, 1953 J. o. JACKSON 2,641,628

POTHEAD Filed April 5, 1948 2 Sheets-Sheet 2 INVENTOR.

Patented June 9, 1953 POTHEAD James 0. Jackson, Grafton, Pa., assignor to Pittsburgh-Des Moines Company, a corporation of Pennsylvania Application April 5, 1948, Serial No. 18,882

8 Claims.

This invention relates to potheads or electrical terminal structures.

Potheads or electrical terminal structures capable of operating under any desired pressure have long been known but so far as I am aware, no such structure has been capable of operating satisfactorily under both elevated pressures and elevated temperatures.

One object of this invention is to produce improved potheads for conducting electrical energy from an outside source to electrical equipment located within a hollow structure such as a heat accumulator and exchanger, or the like operated at elevated temperatures and pressures.

Another object is to produce an improved means for conducting electrical energy from an outside source to resistance heating elements located within a heat exchanger and accumulator or the like operated at elevated temperatures and superatmospheric pressure.

These and other objects I attain by means of the structures described in the specification and illustrated in the drawings accompanying and forming part of this application.

In the drawings:

Figure l is a view partially in longitudinal section and partially in elevation of a pothead structure embodying this invention;

Fig. 2 is an enlarged fragmentary view'partially in section and partially in elevation of a portion of the pothead structure of Fig. 1;

Fig. 3 is an enlarged cross sectional view of a portion of the pothead structure of this invention; and

Fig. 4 is an enlarged view partially in elevation and partially in section of a modified form of pothead embodying certain features of this invention.

The pothead of this invention is designed to conduct electrical energy to electrical equipment located within a hollow structure operating at elevated pressures and elevated temperatures, a structure such as the heat accumulator and exchanger of my application Serial No. 10,139, now Patent 2,556,495.

In a, general way, the pothead of this invention comprises the electrical conductors which extend outwardly from bus bars or other equipment within the hollow structure, through an opening in a wall of such structure and to an appreciable distance beyond such wall; a diaphragm through which such conductors or extensions of such conductors extend; a metal conduit surrounding and spaced from such conductors and having one end thereof secured to the wall of the hollow structure around the opening through which the conductors pass (the opposite end of such conduit having connection with such diaphragm in a pressure-tight manner), and means for sealing the openings in the diaphragm surrounding the conductors or their extensions whereby the interior of the conduitwhich is open to the pressure within the hollow structure-is sealed from the atmosphere by means of such diaphragm and such sealing means.

Referring to Figs. 1 to 3 of the drawings, I0 represents a metal wall of a hollow structure operating at elevated pressure and temperatures, such a structure as the heat accumulator and exchanger of my said application. Such wall is provided with an opening II through which the three conductors I2- extend. These conductors which are subjected to the high temperatures within the hollow structure (heat accumulator and exchanger), are preferably made from a material having resistance to corrosion at the operating temperatures and having relatively high resistance to thermal conduction. A chromium nickel iron alloy of the 18-8 type meets these requirements admirably. Alloys of the 18-8 type contain about 18% chromium and 8% nickel with the balance principally iron.

Conductors I2 are straight and parallel for an appreciable distance, and then each is provided with a bend I3 adjacent its outer end. The outer end of each conductor I2 is welded as at I 4 to the head l5 of a metallic bolt I 6. These bolts extend through openings formed for their reception in a diaphragm I! which is preferably made from electrical insulating material such as Micarta which is a phenolic condensation prodnot.

A metallic conduit preferably comprising three sections I8, l9 and 20, has its inner end welded, as at 2|, to wall I0 surrounding opening H. Conduit sections I8 and I9 are provided with cooperating fianges 22 and 23 between which a heat resisting gasket 24 is secured by the flange bolts 25. Conduit section 20, which is Welded to the outer end of section I9 as at 26, flares outwardly and has its outer end welded to a flange 2'! which extends at right angles to the major axis of the conduit and is provided with a circular row of holes for receiving bolts 28.

Bolts I -6 extend through openings in diaphragm I1 and a heat resisting gasket 29 is positioned between the head I5 of each such bolt and diaphragm I1. A metallic washer 3t surrounds each bolt on the opposite side of the diaphragm from gaskets 29 and the bolts are pulled up tightly to a flange 35 similar to flange 2'1 and pressuretight gaskets 36 are positioned between diaphragm I1 and flanges 21 and 35.

In order to keep conductors l2 separated from one another and from the conduit so that they are electrically insulated from one another and from the conduit, sections l8 and is of the conduit are filled with closely packed cylindrical disks Bl formed of material which is an electrical insulator and also a heat conductor, a material such as Mycalex which is a composition containing mica and lead borate glass. Disks 3i as shown in Fig. 3 are provided with three holes for the three conductors which, within sections [3 and Is of the conduit, are triangularly arranged. Disks 3'! are preferably slipped over conductors i2 before such conductors are welded or otherwise connected to the bus bars or other equipment within the hollow structure.

An electrical conductor 38 (copper cable or the like) is preferably silver brazed, as at 39, into a hole formed for its reception in the outer end of each connecting lug 32.

. In one installation in which I used a pothead such'as disclosed in Figs. 1-3 for conducting electric current to bus bars located within a heat aecumulator and exchanger such as disclosed in said application, the pothead has to operate under temperatures ranging up to 550 F. and under a pressure of 110 pounds per square inch auge.

In such installation, the conductors i2, arranged as disclosed in Fig. 3, are 1% inches in diameter. These and bolts it, which are also 1% inches in diameter and are made from a chromium nickel iron alloy of the 18-8 type.

Sections [8 and IQ of the conduit are made from five inch nominal pipe size steel pipe. Disks 3'! are Mycalax and are about 4% inches in diameter and one inch thick. They are packed closely together and entirely fill sections [8 and H! of the conduit. The distance between flanges 23 and 21 is approximately 6 feet. Connection 34 is coupled to a power conduit (not shown) which supplies the electrical energy required for resistance heating units located within the heat accumulator and exchanger. Such conduit carries about 210 kw. on a 60 cycle, 3 phase 220 volt A. C. circuit.

Diaphragm I? which is made of Micarta is approximately 1 /2 inches thick and. in order to maintain its mechanical strength is necessary to establish a relatively large drop; in temperature between the heat accumulator and ex changer and such diaphragm. This is accomplished partly by the long conduit and partly by disks 3'! which conduct heat from conductors 12 to the conduit wall through which it passes to the atmosphere.

The length of the conduit to be used depends. on the temperature drop required. The longer the conduit, the greater will be the temperature drop. Although a metallic conduit is a fairly 4. good conductor of heat, a relatively long conduit affords a barrier to heat flow from the hot hollow structure to diaphragm l'l.

Where space limitations prevent the use of a relatively long conduit, a shorter conduit provided with heat radiating fins for dissipating the heat to the atmosphere by radiation and convection may be found suitable. In the modified structure of Fig. 4, a steel diaphragm ll'a formed as a section of a hollow sphere, is welded to flange 21a, such flange being Welded to the large end of conduit section 2 Conductors I2 instead of being bent as in Fig. l, have their ends spread apart and welded to bolts it which extend through openings in the diaphragm.

Flanged bushings 4!! made of flexible electrically insulating material are inserted through the openings in the diaphragm either before bolts 5, which form extensions of conductors l2, are inserted through such openings or they may be placed on the bolts before they are inserted. Flexible electrically insulating washers or gaskets 6| surround the extended ends of such bushings, and, with such bushings form flexible electrically insulating spool-like seals. Metallic Washer 3i] bears against the outer face of each flexible washer or gasket 4| and when metallic nuts 3! are screwed home, since they bear against metallic washers 30, the openings in the diaphragm around conductors R2 are effectively sealed against the pressures. Within the conduit and in this manner, the interior of the conduit is sealed from the atmosphere.

Connecting lugs 32 into which the power cables are brazed are secured on bolts It; as in the preferred embodiment of the invention as shown in Figs. 1-3.

A housing member 42 takes the place of re duced section 33 of Fig. 1 and is provided with a flange 43 which, is bolted to flange 21; a flexible gasket 54 being positioned between such flanges and held in place by bolts 45.

What I claim is: I

1. In a device for transmitting electric current to the interior of a hollow structure adapted to operate at elevated temperatures and in combination with such a hollow structure, multiple. spaced bare electrical conductors which are subjected to such elevated temperatures and extend outwardly from the interior of such hollow structure through and beyond an opening in one of its walls and which throughout the major part of their length beyond such wall are straight and parallel and have their outer ends spread apart; a diaphragm through which such spread apart ends extend, a metallic conduit comprising a straight portion, which surrounds and parallels the straight portions of such conductors, and a flaring outer end portion, which surrounds and is spaced from the spread apart ends of such conductors and connects with an outer peripheral portion of such diaphragm, and

multiple disks of electrically insulating and heatv conducting material having substantially flat parallel ends and being provided with through openings for said electrical conductors which are located on the straight parallel portions of such conductors, contact the inner surface of the straight portion of such conduit, and substane tially fill such straight portion so that a relatively large drop in temperature occurs in the electrical conductors between the point at which each passes through the opening in the wall of the hollow structure and the point at which each enters such diaphragm.

2. A structure as defined in claim 1, in which the diaphragm is metallic and insulating means are provided forming pressure-tight joints between such conductors and such diaphragm.

3. A structure as defind in claim 1, in which there are three metallic electrical conductors within the conduit and these parallel one another throughout the major part of their lengths and are so arranged that straight lines connecting their axes and lying in a plane perpendicular thereto define an equilateral triangle.

4. A structure as defined in claim 1 in which the metallic conduit has one end thereof attached in a pressure-tight manner to the wall of the hollow structure surrounding the conductor opening therein and the opposite end thereof is secured in a fluid-tight manner to the outer peripheral portion of the diaphragm.

5. A structure as defined in claim 1, in which the joints between the conductors and walls of the openings in the diaphragm for such conductors are sealed in a pressure-tight manner.

6. A structure as defined in claim 1 in which the conductors are made from a chromium nickel iron alloy of the 18-8 type.

7. A structure as defined in claim 1 in which the diaphragm is formed of a phenolic condensation product.

6 8. A structure as defined in claim 1 in which the cylindrical disks are made from a composition of mica and lead borate glass.

JAMES O. JACKSON.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 251,729 Patterson Jan. 3, 1882 266,353 Delany Oct. 24, 1882 1,152,005 Clark Aug. 31, 1915 1,176,739 Davis Mar. 28, 1916 1,802,584 Steinmayer Apr. 28, 1931 1,889,545 Edmonds Nov. 29, 1932 1,974,298 Case Sept. 18, 1934 1,996,646 Juthe et al Apr. 2, 1936 2,179,781 Frankel et al. Nov. 14, 1939 2,247,671 Tepel July 1, 1941 2,253,981 Peyches Aug. 26, 1941 2,295,214 Jackson Sept. 8, 1942 2,323,792 Cattaneo July 6, 1943 2,329,961 Walker Sept. 21, 1943 2,381,218 Jacob Aug. 7, 1945 2,439,394 Lanzallotti et al. Apr. 13, 1948 FOREIGN PATENTS Number Country Date 239,442 Switzerland Feb. 1, 1946 372,343 Germany Mar. 26, 1923 

